Air-cooled piston



Oct. 27, 1936. H. P. MILLER AIR-COOLED. PISTON Filed oct. 1934 P /VLEZ H15 ATTORNEY Patented Oct. 27, 1936 ITED STATES PATENT OFFICE Claims.

My invention relates to machines employing pistons and cylinders, such as internal combustion engines, steam engines, compressors or vacuum pumps, and more particularly to improve- 5 ments in the cooling of such mechanisms.

t is among the objects of my invention to provide means for effecting a circulation of air through the piston to assist in carrying olf heat developed in the cylinder.

Another object of my invention is to utilize the reciprocation of the piston to effect a forced draft of air through the piston.

Still another object of my invention, relating particularly to compressors and Vacuum pumps,

is to provide means for effecting the forced draft by intaking or discharging the air through the piston.

A still further object of my invention is to provide a reciprocating mechanism of the character o described which is characterized by a ruggedness of design and simplicity of construction.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of my invention. It is to be'understood that I do not limit myself to this disclosure of species of my invention, as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure 1 is a vertical sectional view of a mechanism embodying the improvements of my invention; and

Figure 2 is a. similar View showing a modified form of construction.

In terms of broad inclusion, the reciprocating mechanism embodying my invention comprises an open ended cylinder, a hollow piston slidable in the cylinder, and a valve in the piston for controlling the passage of air through the piston. The valve end of the piston preferably reciprocates in a reduced portion of the working cylinder, and a valve is provided in the reduced cylindrical portion to provide a pump, whereby a forced draft of air is circulated through the piston toeifect the cooling thereof. In mechanisms o-f the compressor and vacuum pump type the valve end of the pisto-n preferably reciprocates directly in the working cylinder, the forced draft being effected simply by intaking or discharging the air through 50 the piston.

In greater detail, and referring particularly to Figure l of the drawing, a preferred type of mechanism embodying the improvements of my invention comprises a working cylinder 2 in which is 55 slidably mounted a working piston 3` Reduced cylindrical portions 4 and 6 are preferably provided at each end of the working cylinder 2, these reduced Vportions being preferably formed as an integral part of the cylinder heads 'I and 8` respectively. 5

In the mechanism illustrated, which may be the cylinder of a double-acting internal combustion engine, the lower reduced cylindrical portion 6 is shown to be mounted directly on the crank case 9v of the engine. The other elements of the engine, 10 such as the intake and exhaust valve, ignition system, etc., are omitted in order to avoid complicating the drawing; it being understood that these elements would be provided for accomplishing their usual functions and in the usual manner. 15 As shown in Figure 1 the lower reduced cylinder portion 6 is open ended and communicates with the atmosphere in the crank case 9. The upper cylinder portion d however is closed by a suitable cover plate I I having a suitable spring pressed 20 check valve I2 mounted thereon. This valve seats on the head of the cylinder and controls the discharge port I3.

The working piston 3 is of hollow construction and is provided at the ends thereof with the 25 reduced piston portions I4 and I6 adapted to slide in the reduced cylinder portions, 4 and 6 respectively. These reduced piston portions are also hollow and communicate with the internal cavity of the working piston 3, and the lower piston 30 portion I6 is of open ended construction to provide an opening directly with the atmosphere. Suitable rings I1 are provided on the working piston 3 as well as on the reduced piston portions Ill and i6, and a suitable connecting rod I8 is connected in the lower open end of the piston portion I6 by a. suitable wrist pin I9 in the usual manner of mounting pistons on the upper ends of connecting rods.

The upper end of the piston portion I -'I is closed to provide a working face 21|, and a suitable spring pressed check valve 22 is mounted on the end of the piston. This valve is seated on the upper or inner surface of the piston, and is provided to control the intake port 123 `communicating Vbe- 451.:

tween the chamber of the cylinder portion 4 and the cavity provided by the hollow piston.

By this arrangement of mechanical parts the upper cylinder portion 4 is in effect a pumping cylinder, and when the piston reciprocates air is drawn into the pumping cylinder through the intake port 23 and then forced out through the discharge port I3. As this pumping takes place a forced draft of air is created through the piston, and this air circulation operates to carry off heat developed in the cylinder. It will also be observed that the air is drawn from the crank case, so that an air draft is also created which operates to cool the oil; it being understood that suitable ventilators are provided in the crank case for introducing the air which is subsequently pumped up through the piston.

Since a water cooling system is not required with this type of engine construction the water jackets characterizing such systems are not shown. Instead, air cooling fins 24 are shown as being preferably employed for assisting in the air cooling of the cylinder. As has already been stated, the mechanism of Figure l is illustrated as comprising the cylinder of a double-acting internal combustion engine. In such an engine I preferably provide annular grooves 26 in the Working faces of the working piston 3. The gas spaces provided by these annular grooves are especially desirable when the mechanism is used in a two-cycle internal combustion engine of the Diesel type, since they create a lesser tendency on the part of the incoming charge of air to mix with the outgoing burnt gases. That is, these annular shapes provide less frontage between the live and dead gases, so that there is a less tendency to churn and mix. This leads to greater fuel economy. Y

If desired the upper cylinder portion 4 and the upper piston portion I4 may also be of open ended construction, and an air draft created through the piston by external means, such as compressed air injected into the crank case of the engine.

It is to be understood however that the general arrangement of mechanism as shown in Figure 1 may be incorporated in any type of reciprocating mechanism, and the principle of internal air cooling is just as effective in an air compressor or a vacuum pump as in a combustion engine.

Figure 2 illustrates a modification of my invention, as particularly adapted to compressors and vacuum pumps. In this case a working piston 21 is slidably mounted in a working cylinder 28. In the compressor type of machine, as illustrated, the upper and lower cylinder heads are each provided with discharge ducts 2S. A reduced portion 30 is provided at the lower end of the working cylinder, and this portion is preferably mounted on a suitable support 3l. The lower end of the piston 21 is also provided with a reduced portion 32 adapted to slide in the cylinder portion 30, and the piston portion 32 as well as the working piston 21 are provided with suitable rings 33.

In this construction the working piston 21 is hollow, as is the reduced piston portion 32, and the latter portion as well as the cylinder portion 30 are open ended; the connecting rod 34 being secured in the open end of the piston portion 32. Suitable spring pressed check valves 36 and 31 are mounted on the ends of the working piston 21, and these valves are arranged to control suitable intake ports 38 and 39 communicating between the internal cavity of the piston and the ends of the working cylinder. In other words, in this construction the air is drawn into the cylinder through the piston and then is forced out of the cylinder through the discharge ducts 29. By this arrangement a forced draft of air is being constantly maintained through the pistons, which draft operates to dissipate the heat being developed in the cylinder and pistons.

I claim:

1. A reciprocating mechanism comprising a cylinder having reduced portions adjacent the ends thereof, one of said reduced portions being open ended, a hollow piston slidable in the cylinder and having reduced portions slidable in said reduced cylinder portions, the piston portion in the open ended cylinder portion also having an open end, a valve in the end of the other piston portion, and a valve in the cylinder portion in which said latter piston portion slides.

2. A reciprocating mechanism comprising a working cylinder, a hollow piston slidable in said cylinder and having an open end communicating with the atmosphere, a pumping cylinder connected with said working cylinder, a hollow eX- tension on the working piston and providing a piston for said pumping cylinder, a check valve in the pumping piston, and a check valve in the pumping cylinder.

3. In combination a crank case, a cylinder mounted on the crank case, a head on the cylinder, a hollow piston slidable in the cylinder and having an open end communicating with the interior of the crank case, a hollow cylindrical extension on the upper end of the piston and slidably mounted in the cylinder head, said piston extension having a diameter less than that of the cylinder, and the outer end of the piston extension having an opening, whereby a passage is provided for air circulation from the crank case and out through the top of the piston.

4. In combination, a crank case, a cylinder mounted on the crank case, a hollow piston slidable in the cylinder, a head on each end of the cylinder, hollow cylindrical extensions on each end of the piston and slidably mounted in the cylinder heads, said piston extensions having a diameter less than that of the cylinder, the lower piston extension having an open end communicating with the interior of the crank case and the outer end of the upper piston extension having an opening, whereby a passage is provided for air circulation from the crank case and out through the top of the piston.

5. In combination, a crank case, a cylinder mounted on the crank case, a head on the cylinder, a, hollow piston slidable in the cylinder and having an open end communicating with the interior of the crank case, a hollow cylindrical extension on the upper end of the piston and slidably mounted in the cylinder head, said piston extension having a diameter less than that of the cylinder, and means for circulating air through the crank case and through said piston and piston extension.

HORACE P. MILLER. 

